Continuous manufacture of silicone coploymers

ABSTRACT

Disclosed is a continuous process for producing silicone copolymers using a series of at least one stirred-tank reactor, the last of which reactors in said series has crude product stream feeding into at least one plug flow reactor, wherein this crude product stream is sufficiently homogeneous that this stream which undergoes further reaction in the plug flow reactor does not undergo phase separation.

FIELD OF THE INVENTION

The present invention relates to a process for the continuous productionof silicone copolymers, and to the novel products produced by theprocess.

BACKGROUND OF THE INVENTION

Silicone copolymers serve as surface-tension lowering agents inagricultural adjuvants, stabilizers for polyurethane foam, additives forcoatings applications, antifoams, and emulsifiers. The efficientmanufacture of silicone copolymers is desired for two primaryreasons--lower cost, and less waste. If, in addition, the equipmentneeded for that method or process is less costly to construct, suchmethod or process would be inherently attractive. Moreover, thereremains a need for a process to prepare silicone copolymers thatprovides desirable properties in the application for which they areintended, which process would offer manufacturers the flexibility toproduce variations of products, determined by the choice of method ofmanufacture.

Chemical reactions may be conducted in a batch fashion, in a continuousfashion, or in hybrid fashion partially batch or partially continuous).For example, the reactants necessary to prepare a silicone copolymer maybe a silicone fluid containing one or more hydrogen atoms directlybonded to silicon (hereafter referred to as a hydrogen siloxane or SiHfluid); and an olefinically terminated compound (hereinafter referred toas an olefinic compound). The two components are mixed together inappropriate amounts, and while being sufficiently agitated, catalyst isadded. A vigorous reaction ensues, and the olefin, by hydrosilation,becomes chemically attached to the silicone.

Because in most cases the hydrogen siloxane fluid and the olefiniccompound are immiscible, a compatibilizing agent frequently is used tofacilitate reaction. This agent is often called a solvent, although itis not necessary to use it in sufficient quantity to dissolve bothcomponents. If the hydrogen siloxane fluid and olefinic compound aresufficiently pure of minor-to-trace components, the amount of "solvent"can be decreased, in some cases to zero. However, in those cases, goodagitation becomes even more important, to maximize the contact betweenthe two (relatively) immiscible phases.

The reaction between the raw materials need not be conducted in a purelybatch fashion. For example, if the reactivity of the hydrogen siloxanefluid is very high, the olefinic compound may be charged to the reactorin its entirety, a fraction of the hydrogen siloxane fluid may becharged, the reaction catalyzed by adding a noble metal catalystsolution, and the remaining hydrogen siloxane fluid added subsequentlyand at such a rate, after the initial reaction exotherm has begun tosubside, as to keep the reaction under control. This process issometimes called semi-batch, or (incorrectly) semi-continuous. If boththe hydrogen siloxane fluid and the olefinic compound are added only inpart initially, and then all components added continuously after thereaction is initiated, and added until the reactor is full, the reactionis called (correctly) semi-continuous.

Truly continuous reaction of hydrogen siloxane fluid and olefin has,heretofore, not been successfully accomplished. This is for severalreasons, which will be enumerated in detail.

There are two main types of continuous reactors for liquid phasesystems: continuous stirred tank reactors (known as CSTRs); andplug-flow reactors. In CSTRs, it is inherent that not all of any of thereactants can be consumed completely. However, silicone copolymercontaining unreacted hydrogen siloxane fluid is unsuitable for makingmany commercial products. Thus, CSTRs themselves are not good for makingsilicone copolymer.

The presence of this unreacted hydrogen siloxane fluid exiting a CSTRreaction might be circumvented by the use of a plug flow reactor;however, without the continual mixing of the CSTR the immisciblehydrogen siloxane fluid and olefinic compound will phase-separate veryrapidly subsequent to initial mixing, thus causing the reaction toproceed more and more slowly. In fact, the reaction ceases rapidlywithout ongoing agitation, and then fails to proceed, even upon renewedagitation, which effect is believed to be caused by gradual,irreversible deactivation of the catalyst. Thus, neither of the twostandard continuous reactor systems alone is effective for themanufacture of silicone copolymers.

BRIEF SUMMARY OF THE INVENTION

Silicone copolymers exhibiting improved properties can be manufacturedin continuous fashion by using a series of at least one CSTR followed byat least one plug flow reactor. It has been found that the siliconecopolymers produced in this continuous fashion may have certainproperties markedly different from those of analogous copolymersproduced in batch fashion.

Thus, a process for producing silicone copolymers is taught having thesteps of,

(a) continuously feeding hydrogen siloxane, olefinically substitutedcompound capable of reacting with said hydrogen siloxane, and catalystfor said reaction, to at least one (1) CSTR in series and continuouslywithdrawing from the last CSTR in said series a crude product streamthat contains silicone copolymer and unreacted hydrogen siloxane andolefinic compound, provided that said hydrogen siloxane and saidolefinic compound are reacted in said series of CSTRs to a sufficientextent that said crude product stream is sufficiently homogeneous thatit does not undergo phase separation in step (b), and

(b) continuously feeding said crude product stream to at least one plugflow reactor from which product is withdrawn.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an exemplary production system for the manufacture of siliconecopolymers.

DETAILED DESCRIPTION OF THE INVENTION

Continuous systems are smaller than batch reactor systems, are lesscostly, contain less product, are easier to clean, generate less waste(if cleaning is implemented between using the reactor system to make twodifferent products), and less material is lost from equipment "holdup",so overall efficiency is higher. From an operating perspective,continuous systems are also more "controllable", in the sense that theextent or degree of reaction primarily is determined by the reactor orequipment design, as opposed to elapsed time.

Neither a CSTR nor a plug-flow reactor, alone, provides for continuousmanufacture of suitable silicone copolymers; however, when used incombination, the reactor system of the present invention is surprisinglyeffective at driving the reaction to completion, without undergoing thephenomenon of phase separation, and the resultant copolymer providesunanticipated additional benefits.

Reactants

The present invention is applicable to any hydrosilation reaction,typically catalyzed, between a hydrogen siloxane (or SiH fluid) and anolefinically unsaturated compound (hereinafter referred to as olefiniccompound). The hydrogen siloxane can be an organohydrogensiloxanecomprising any combination of siloxane units selected from the groupconsisting of R₃ SiO_(1/2), R₂ HSiO_(1/2), R₂ SiO_(2/2), RHSiO_(2/2),SiO_(4/2), HSiO_(3/2) and RSiO_(3/2), provided that the hydrogensiloxane contains sufficient R-containing siloxane units to provide anaverage from 1.0 to 3.0 R radicals per silicon atom and sufficientH-containing siloxane units to provide from 0.01 to 1.0 silicon-bondedhydrogen atoms per silicon atom and a total of R radicals andsilicon-bonded hydrogen atoms of from 1.5 to 3.0 per silicon atom.

Alternatively, wherein M=(R)₃ SiO_(1/2), M'=(R)₂ HSiO_(1/2), D=(R)₂ SiO,D'=(R)HSiO, and x and y are integers, the preferable structures of theSiH fluid would be MD,D'_(Y) M wherein x and y are in the respectiveranges of 0≦×<160, 1<y<40, and 1≦x+y<200, and MD_(x) D'_(y) M' orM'D_(x) D'_(y) M' wherein x and y are in the respective ranges of0≦x≦160, 0≦y≦40 and x+y≦200. The polymer formulae given here andelsewhere herein, such as MD_(x) D'_(y) M, are to be understood asrepresenting the average compositions of statistical polymers, unlessotherwise noted. Some preferred SiH fluids are MD'M and M'D M'trisiloxanes.

Each R group is independently the same or different and each representsa hydrocarbon radical or an alkoxy or polyalkyleneoxy radical.Illustrative of suitable R radicals are C₁ to C₁₂ alkyl radicals (suchas methyl, ethyl, propyl, butyl, isopentyl, n-hexyl, and decyl);cycloaliphatic radicals containing 5 to 12 carbon atoms (such ascyclohexyl and cyclooctyl); aralkyl radicals (such as phenylethyl); andaryl radicals (such as phenyl optionally substituted with 1 to 6 alkylgroups of up to 6 carbon atoms, such as tolyl and xylyl). Alsoillustrative R radicals are C₁ to C₁₂ alkoxyl radicals such as methoxy,ethoxy, propoxy, butoxy, and decyloxy; and polyalkyleneoxy radicals suchas CH₃ O(CH₂ CH₂ O)_(a) (CH₂ CH(CH₃)O)_(b) --, in which the subscripts aand b may vary from 0 to about 200 and a+b>0. The preferred R radical ismethyl.

The SiH fluids are typically fluids with a hydrogen content (measured byreaction with aqueous strong base to liberate hydrogen gas) of fromabout 5 cc/g to about 334 cc/g. The viscosities of the fluids can rangefrom less than 1 cstk (centistoke) to greater than 300 cstk (25° C). Thestructures of these fluids range from pure monomer, such as1,1,2,2-tetramethyldisiloxane (M'M') to polymeric equilibrated fluidhaving a structure of MD₁₅₀ D'₁₀ M. Dimethylhydrogensiloxy-endblockedsiloxanes may also be used to prepare linear block copolymers, sometimesreferred to as (AB)_(n) structures. The SiH fluids may be blends ofdifferent molecular weight and molecular structure fluids. There appearsto be no limit to the structure of the hydrogen siloxane other than thatimposed by handling (practical) aspects such as viscosity, and thedesired properties of the copolymer product.

The reactive substituent is an olefinically substituted moiety.Preferably, the olefinic compound is a polyoxyalkylene reactantcorresponding to the formula R¹ (OC_(a) H_(2a))_(n) OR², it beingunderstood that the polyoxyalkylene moiety can be a block or randomcopolymer of oxyethylene, oxypropylene or oxybutylene units and istypically a blend of molecules of varying chain lengths andcompositions. In the foregoing formula, a is 2 to 4 for each unit, n is1 to 200, R¹ denotes an alkenyl group (preferably an alpha-olefinicgroup) containing 3 to 10 carbon atoms and most preferably an allyl ormethallyl group; and R² denotes a monovalent radical, preferablyhydrogen, an alkyl group containing 1 to 5 carbon atoms, an acyl groupcontaining 2 to 5 carbon atoms, a 2-oxacycloalkyl group of 4 to 6 carbonatoms, or a trialkylsilyl group. Alternatively, if it is desired toprepare an (AB)_(n) type copolymer, R² may be an alkenyl group(preferably an alpha-olefinic group) containing 2 to 10 carbon atoms,and most preferably an allyl or methallyl group.

Structures of the preferred olefinically unsaturated polyether reactantused can typically range from polyalkyleneoxide monoallyl ether ofnominal molecular weight 204 Daltons, all-ethylene oxide; to 8000Daltons, 40% ethylene oxide, 60% propylene oxide; to 1500 Daltonsall-propylene oxide or to 1500 Daltons all-butylene oxide. Whether thepolyether is capped (e.g., a methyl allyl ether) or uncapped (e.g. amonoallyl ether) is immaterial. If the polyether is uncapped, it ispreferred that an appropriate buffering agent be present, such as any ofthose disclosed in U.S. Pat. No. 4,847,398, the disclosure of which ishereby incorporated herein by reference.

Other olefinically unsaturated olefinic compounds useful herein are anolefin-started alkane (e.g., 1-octene, 1-hexene, ethylene,vinylcyclohexane), an olefin-started alcohol, an olefin-substitutedepoxide (e.g., allyl glycidyl ether, or vinylcyclohexene monoxide), avinyl-substituted alkylamine, a halogenated olefin-started alkane, allylmethacrylate, a vinyl-started nitrile (e.g., acrylonitrile) or anacetylenically unsaturated material (e.g., butyne diol). Other specificexamples include 4-methyl-1-pentene, styrene, or eugenol.

Multiple olefinic compounds may be used on one copolymer. For example,ethylene is sometimes used with an allyl-polyether to improvecompatibility as a polyurethane foam surfactant; vinylcyclohexenemonoxide is used as a co-reactant with allyl-polyether to form aterpolymer used in textile softening; and eugenol and a polyether areused with a hydrogen siloxane fluid to produce a diesel fuel antifoamcopolymer.

The reactants preferably are purified and dried. No compatibilizingagent or "solvent", is needed, but low levels may be added withoutcompromising the effectiveness of the process. However, in that case, asolvent stripping system would need to be incorporated; or the solventwould remain in the copolymer product.

As previously indicated, the hydrosilation reaction is conducted in thepresence of a hydrosilation catalyst, preferably containing a noblemetal. Thus, the hydrosilation reaction between the hydrogen siloxaneand the olefinically unsaturated reactant is facilitated by usingcatalytic amounts (or effective amounts) of a noble metal-containingcatalyst. Such catalysts are well known and include platinum, palladiumand rhodium-containing compounds. They are reviewed in the compendium,Comprehensive Handbook on Hydrosilylation, edited by B. Marciniec andpublished by Pergamon Press, N.Y. 1992. In general, platinum catalystsare preferred, and chloroplatinic acid and the platinum complexes of1,3-divinyltetramethyldisiloxane are particularly preferred.

The catalyst is employed in an effective amount sufficient to initiate,sustain and complete the hydrosilation reaction. The amount of catalystis usually within the range of from about 1 to about 100 parts permillion (ppm) of noble metal, based on the total parts of the mixture ofreactants and solvent. Catalyst concentrations of 2-20 ppm arepreferred.

The hydrosilation reaction optionally can be conducted in the presenceof additives (or "buffering" agents) such as the carboxylic acid saltsdisclosed in U.S. Pat. No. 4,847,398. In that patent, the use of"buffering" salts is disclosed, which salts have the effect ofpreventing the dehydrocondensation of hydroxyl groups with the SiHmoiety. The salt preferably is predissolved in the polyether, prior tointroduction into the CSTR. The concentration used, the salt or otherbuffer selected, and the effects expected are process specific.

The hydrosilation reaction optionally can be carried out in the presenceof the sterically hindered nitrogen compounds disclosed in U.S. Pat. No.5,191,103, or the phosphate salts disclosed in U.S. Pat. No. 5,159,096.Depending on the method of manufacture, and on the nature of thereactants, one or more of these additives may be present during thehydrosilation reaction. For example, a low, but sometimes adequate,level of carboxylic acid salts or phosphate salts already may be presentin olefinically substituted polyoxyalkylenes following capping ofhydroxyl-terminated allyl-started polyoxyalkylenes with allylic,methallylic, methyl or acyl groups, or due to neutralization of basiccatalysts with phosphoric acid. In such instances, the use of additionalsalt or other additive may not be necessary to achieve the desiredeffect.

One potential product is a silicone polymer of the structure M*D_(x)D*_(y) M*,

wherein

M* is SiO_(1/2) (CH₃)₂ R* or O_(1/2) Si(CH₃)₃ ;

D is as above;

D* is SiO2/2(CH₃)R*;

R* is derived from the olefinic compound discussed above by addition ofan Si-H bond across an olefin moiety of the olefinic compound, whereineach R* may be the same or different; and

x and y are as above.

Alternatively if an [AB]_(n) type copolymer is produced, it will be ofthe structure [--B--[SiO (CH₃)₂ ]n--]m wherein B is the substituent(except derived from a di-olefin or similar di-functional startingmaterial), n is 1 to 500 and m is 2 to 500. Moreover, variations on theabove structures, e.g., using cyclic siloxanes or using branchedsiloxanes containing SiO_(4/2), SiHO_(3/2), or Si(CH₃)O_(3/2) groups,may be produced.

Equipment

The present invention is carried out using at least one, and preferablytwo, CSTRs connected in series. These can be of any conventional designeffective to carry out the desired reaction. Each is equipped with inletfor the reactants, outlet for the product stream, and agitator. Theoutlet of the last stirred tank reactor in the series is connected tothe inlet of a plug flow reactor which also can be of any conventionaldesign effective to carry out the desired reaction. The term plug flowreactor includes the functional equivalent thereof which may be a seriesof CSTRs, though a plug flow reactor is preferred. See Hill, AnIntroduction to Chemical Engineering Kinetics and Reactor Design, pp.279-299 (1977), which is incorporated herein by reference.

The number of CSTRs will depend somewhat on the identity of theparticular reactants and on the desired rate of throughput. For somecases, it has been found that one CSTR is sufficient, e.g., trisiloxanefluids. For most reactions, formation of the desired silicone copolymerproceeds at a rate such that two CSTRs are needed. In other reactions,three or even four (and rarely, more) CSTRs are needed. The number ofCSTRs needed is related generally to the "clear point" of a batchreaction of the reactants, as discussed below. In any case, the outletof the first CSTR feeds directly to the inlet of the second CSTR, theoutlet of the second CSTR feeds directly to the inlet of the third CSTRif one is present, and so on.

The design of the CSTRs and plug flow reactors is well-known in the art,and is summarized, for example in "An Introduction to ChemicalEngineering Kinetics and Reactor Design" John Wiley & Sons, N.Y., 1977,pages 245-304.

With reference to the Figure, there is an hydrogen siloxane fluid feedline 1, an olefinic compound feed line 2 and a catalyst feed line 3. Itis preferred to pre-heat the olefinic compound in a heat exchanger 4.There is a first CSTR 5, which has a product withdrawal stream 6, whichfeeds to an optionally present second CSTR 7. The exit stream of thesecond CSTR 8 feeds to a plug flow reactor 9, which feeds 10 to aproduct separator 11. The light products are withdrawn 12 while theheavy products 13 are cooled in a heat exchanger 14. Final copolymerproduct may be collected in storage 15.

Operation

At steady state, the reactants are fed continuously to at least thefirst CSTR in the series. Catalyst also can be fed continuously, orintermittently. As will be described more fully below, one or bothreactants and/or additional catalyst also can be fed to the secondand/or successive CSTRs. Preferably, the total amount of the olefiniccompound(s) fed to the process represents a stoichiometric excess basedon the total amount of hydrogen siloxane fed, since it is preferred thatthe silicone copolymer product contain no more than a trace amount ofunreacted hydrogen siloxane (i.e., less than 0.1 cc/g hydrogen content,as described above), and preferably no unreacted hydrogen siloxane atall.

The stream that exits the first CSTR and enters the second CSTR (ifused) contains reaction product(s), or partial reaction product(s)(i.e., molecules still containing some SiH moieties), unreacted hydrogensiloxane and olefin, and amounts of catalyst, and the reaction thereofcontinues in the second CSTR. If the residence time in the series ofCSTRs is prolonged, the catalyst may no longer be active when thereaction mixture enters the plug flow reactor. The time required forthis to occur is dependent on variables such as the identity and thepurity of the olefinic compound, and is thus peculiar to everyindividual reaction system. In general, however, it is desirable to havenot less than 50% by weight, and no greater than 90% by weight of thelimiting reagent reacted in any given CSTR. The remainder of thereaction will be completed in the plug flow reactor. Additional catalystoptionally can be added after the first CSTR, i.e., to the second, oroptionally third or later, CSTRs, to accomplish a greater degree ofreaction.

In a preferred embodiment, the reaction proceeds in the series of CSTRsto such an extent that the stream (termed the "crude product stream")exiting the last CSTR is homogeneous. The crude product stream isconsidered to be sufficiently homogeneous if it does not undergo phaseseparation as it continues to react under laminar flow conditions in theplug flow reactor. It has been found, quite surprisingly, that thisdegree of homogeneity can be achieved in the series of CSTRs in spite ofthe incompatible natures of the hydrogen siloxane and the reactiveolefinic compound reactants, and in spite of the fact that there may beresidual amounts of unreacted silanic hydrogen and olefinic compound ineven the last of a series of two or more CSTRs. It has also been found,all the more surprisingly, that even if it is visibly cloudy when itexits the last CSTR, the crude product stream does retain itshomogeneity through the plug flow reactor without undergoing the phaseseparation.

The point at which the crude product reaches homogeneity oftencorresponds to about 60-75%, conversion, though sometimes lower, of thehydrogen siloxane to silicone copolymer. This point is sometimesreferred to as the "clear point".

The number of CSTRs required in the series generally is related to theclear point of a batch reaction conducted on the same reactants as willbe used in the continuous process of the present invention. If the clearpoint occurs at less than 50% reaction, a single CSTR in the series maysuffice. However, for general processing of a variety of copolymers, aseries of at least two CSTRs is preferred, to achieve the degree ofhomogeneity described above. In those cases where the clear point occursat greater than 90% reaction, a third CSTR may be required. If stagedaddition, described below, is used, then a third reactor may berequired. However, unless staged addition is desired, a third reactor isnot generally required. By decreasing the flow rates to the first CSTR,a third CSTR may be avoided; but because of phase separation which willoccur prior to the clear point, it is preferable to use a second CSTR.

To help ensure that the product stream has passed the clear point, it ispreferred to carry out the reaction in the series of CSTRs underconditions such that the stream that exits the next-to-last tank of theseries is visibly homogeneous. As noted, the stream still containsunreacted material and so continues to react in the last CSTR even afterhaving attained homogeneity.

Since catalyst deactivation proceeds rapidly at the end of the reaction,and because in an idealized CSTR some unreacted components are alwayspresent in the exiting mixture, it is preferred that the completion ofreaction occur in the plug flow portion of the system. Thus, the crudeproduct stream does not need to have been taken exhaustively tocompletion of the reaction in the CSTR series to form siliconecopolymer.

The plug flow reactor should have a flow rate such that there is laminarflow therein. The space time (τ), and therefore reactor size, of thereactor depends on the catalyst concentration used. The temperatureshould be the same as or higher than that in the last CSTR.

Thus, in one embodiment of the invention, a polyether or olefin, orboth, and a hydrogen siloxane fluid are metered into a first CSTR, andthe temperature of the contents is raised to and maintained at between45° C. and 135° C. When the first CSTR is half-to-completely full, flowof the hydrogen siloxane fluid, polyether and olefinic compound isstopped, and catalyst is added rapidly, a large enough aliquot initiallyto take the entire contents to the desired concentration of noble metalor other active catalytic species, and afterwards sufficient only tomaintain that concentration. After catalyst addition, an exotherm isobserved in the first CSTR. After the temperature has achieved thedesired set point, flow is begun again of the catalyst, hydrogensiloxane fluid, and olefinic compound(s) into the reactor, and at thesame or a later time, flow begins out of the first CSTR optionally intoa second CSTR of same or similar size. The second CSTR is maintained atan effective reaction temperature, usually the same as or higher thanthe first, but preferably within 25° C. of the temperature in the firstCSTR. Once the second CSTR is full, flow is begun optionally in the samemanner through a third and optionally subsequent CSTR(s), or preferablydirectly to a rising plug flow reactor of volume equal to or greaterthan the prior CSTR, and maintained within the same temperature range,usually the same as or hotter than the second CSTR. Once the plug-flowreactor is full, optionally flow begins to a conventional stripping unitto remove trace volatiles, reducing odor and flammability, or theproduct can be collected and further processed, as for example, byfiltration or stripping elsewhere, if needed. The copolymer exiting theplug flow reactor does not require any further reaction to be suitablefor use.

If a third CSTR is used, it is first filled, and then the flow exits tothe plug flow reactor, as described above. A third CSTR can help obtainphase compatibilization by vigorous mechanical agitation for a longerperiod, or to allow further reaction completion if staged addition(discussed below) is employed in the second CSTR. The need for a thirdCSTR will become apparent if a sample of the reaction mixture exitingthe second CSTR shows evidence of phase separation--for example, thedevelopment of two distinct phases; or if, upon centrifugation to removeair bubbles, the sample remains hazy.

In a preferred embodiment of the reactor system, recirculating loops areprovided between the exit of the first CSTR, back to the inflow, andfrom the exit of the second CSTR (if used), back to the inflow of thefirst CSTR. Such a recycle stream may be used during startup, to reducereactor size requirements, or to return product to an earlier CSTR inthe series. Thus, an infrared or other monitor senses whether theremaining content of hydrogen bound to silicon of the outflow of thesecond CSTR is above a tolerable level, and if so the outflow can bepartially or filly recycled back to the first CSTR, which prevents anyphase separation occurring in the plug-flow reactor. The recycle loopfrom the outflow of the first CSTR back to the inflow can be monitoredby an IR detector also, but is not routinely used in this fashion.Rather, it is used during start-up to ensure that reaction hasprogressed sufficiently before filling the second CSTR.

In the most preferred embodiment, a third CSTR is required only ifstaged addition (described below) is practiced.

In the present invention, consistent introduction of a second olefiniccompound easily is accomplished: it can be added to the second CSTR.Because this second component is not present in the first CSTR, reactionin the first CSTR must occur only between the hydrogen siloxane fluidand the first olefinic compound. Upon entering the second CSTR, thesecond olefinic compound is available to react with the hydrogensiloxane fluid, along with any unreacted first olefinic compound.. Ofcourse, it is not necessary to add either olefinic compound exclusivelyto one CSTR; they may be fed to two or more CSTRs in different ratios.If staged addition is used, it generally is preferred not to add anyadditional reactants to the last in the series of CSTRs. Thus, in athree-CSTR configuration reactants would be added to the first and thesecond CSTRs, in the proportions desired, but not to the third CSTR; thehydrosilation reaction can thus be effectively extended to the degree ofhomogeneity required (as discussed above).

Likewise, it becomes apparent that a second, different hydrogen siloxanefluid can be introduced in similar staged fashion. In fact, anycombination of reactants can be combined in staged fashion, and siliconecopolymer product can be obtained much more reproducibly andconsistently than could be accomplished in a batch mode, unless thedesired products could be obtained in separate batch reactions and thencombined after the reactions are complete.

The copolymers of the present invention may be used as surfactants,antifoams, agricultural adjuvants, textile finishes, reactive dilvents,coating additives, wetting agents, hydrophobizing agents, inter alia, aswill be clear to one of skill in the art.

Some of the copolymers produced by the above-described process can beunique, and can differ significantly in their properties from copolymersmade from the same reactants in batch processes. One manner in whichthis uniqueness appears is in the performance of the copolymer inproduction of polyurethane foam. Silicone copolymers made according tothe present invention can be used in the production of polyurethane foamin the same manner as for known silicone copolymer surfactants. Thus, afoamable mixture is formed comprising a polyol component, apolyisocyanate, one or more catalysts, an optional auxiliary blowingagent, and the silicone copolymer surfactant. The composition is reactedto produce the polyurethane foam.

In comparison to batch-produced copolymer, a continuously producedcopolymer can afford flexible polyurethane foam that has a much greateropen-cell content. With copolymer made by the continuous process, thereappears to be a wider range of potency vis-a-vis breathability (facilityof air flow through the foam); the foam made with this copolymer remainssoft and flexible throughout the surfactant molecular weight range thatis practical based on other considerations such as viscosity.

Thus, by producing the copolymer in continuous fashion in accordancewith the present invention, the manner of combination of the hydrogensiloxane fluid with the olefinic compound appears to have beenunexpectedly altered, consistent with the observed change inbreathability. This discovery, that the mode of synthesis of thecopolymer affects breathability, provides the very significant advantagethat the continuous process of the present invention--particularly ascontrasted to batch mode--can be modified purposefully to cause any of avariety of desired copolymer structures. This aspect may be achieved bycarrying out the process of the present invention using the embodimentreferred to herein as "staged" addition of the reactants.

Continuous copolymer manufacture offers significant new opportunity toconsistently vary the distribution of pendant groups on the copolymer,and thus "tailor" the properties to enhance the desired characteristicsin the application. When using staged addition, a third CSTR ispreferred, allowing a greater degree of reaction completion prior to themixture entering the plug flow reactor. It is also preferred in suchcases to add reactants to all of the CSTRs other than the last one.

EXAMPLES

Whereas the scope of the present invention is set forth in the appendedclaims, the following specific examples illustrate certain aspects ofthe present invention and, more particularly, point out methods ofevaluating the same. It is to be understood, therefore, that theexamples are set forth for illustration only and are not to be construedas limitations on the present invention. All parts and percentages areby weight unless otherwise specified.

The following test procedures were used to evaluate the productsobtained in the examples.

Foam Test

Unless otherwise indicated in the Examples, the polyurethane foams wereprepared according to the general procedure described in "UrethaneChemistry and Applications" K. N. Edwards, Ed., American ChemicalSociety Symposium Series No., 172, A.C.S., Washington, D.C. (1981) pg130 and J. Cellular Plastics, November/-December 1981 pgs. 333-334. Thebasic steps in the procedures for mixing and foaming of blownpolyurethane foam on a laboratory scale are:

1. The formulation ingredients are weighed and made ready to be added inthe predetermined sequence to the mixing container.

2. The formulation ingredients (with the exception of polyisocyanate)are mixed intensively, and allowed to "degas" for a prescribed time; anauxiliary blowing agent, other than water, may be added (if suchauxiliary agent is used) prior to mixing.

3. Polyisocyanate is added and the formulation is mixed again. The mixedformulation is poured quickly into an open-topped container such as anopen-topped disposable plastic pail for slab foam and the foam isallowed to rise.

4. After the rise is complete, the foam is allowed to stand from thetime the mixing procedure began a total of 3 minutes, and is thenpost-cured in an oven at 115° C. for fifteen minutes. Foam Celluniformity (Table 1 ST) is judged by the structure of the foam where a"1" rating has small uniform cell structure and a "14" has largenon-uniform coarse cell structure. Foams were evaluated in duplicate andvalues averaged. Urethane foam Air Flow (Table 1, AF) are obtainedutilizing a NOPCO instrument on a horizontal 1/2 inch (1.27 cm) thickcut of foam obtained three inches from the bottom of the foam bun. ThePorosity of the foam is measured in ft³ /min of air flow through the 1/2inch (1.27 cm) thick cut of foam.

Cloud Point

Cloud point is a measurement of water solubility and as used herein isthe temperature at which a silicone polyether copolymer, for example,begins to precipitate out of a 1% copolymer/99% water solution. Thehigher the cloud point the more prolonged (as temperature increases) thewater solubility.

Cloud Point was determined as follows: A 1-gram of sample was dissolvedin 99 ml of distilled water in a 150 ml beaker. A 1 inch (2.54 cm)plastic coated stirrer bar was inserted in the beaker, and the beakerwas placed on a combination stirrer/hot plate. A 0 to 100° C.thermometer was suspended in the solution with the bulb 1/2 inch (1.27cm) from the bottom of the beaker. With mild stirring, the contents ofthe beaker were heated at the rate of 1 to 2° C. per minute. Thetemperature at which the submerged portion of the thermometer was nolonger visible was recorded.

Viscosity

Viscosity was determined at 25° C., using a calibrated Ostwaldviscometer which gives an efflux time of approximately 100 seconds. Themeasurements are repeated until the efflux time readings agree within0.1 seconds. Calculations are determined by the equation: E×F=Viscosity(cstk), where E=Efflux time in seconds; F=Calibration factor.

EXAMPLES

Examples 1-3 are comparative examples in which the method of preparationutilizes a batch hydrosilation process. Examples 4-6 below, demonstratethe production of Copolymers employing a Continuous hydrosilationprocess utilizing two continuous stirred reactors followed by a plugflow reactor in series. Example 1 (batch) and Example 4 (continuous)utilizes the same raw materials in the same stoichiometric ratios. Theolefinically substituted polyether is uncapped and possesses hydroxylfunctionality. This material is used in cosmetic formulations in whichhigher water solubilities and higher cloud points are desirable.

Example 2 (batch) and Example 5 (continuous) utilize the same rawmaterials in the same stoichiometric ratios. These examples utilizeolefinically substituted polyethers which are methyl terminated. Theseproducts are used in flexible polyurethane foam formulations in whichgood uniform cell structure and open (as measured by higher air flow)cell structure is important.

Example 3 (batch) and Example 6 (continuous) utilize the same rawmaterials in the same stoichiometric ratios. These examples teachutilizing olefinically substituted polyethers which are Acetoxyterminated. These products are also used in flexible polyurethane foamformulations and as noted good uniform open cell structure is desirable.

List of Materials and Abbreviations

M=(CH₃)₃ SiO_(1/2), D=(CH₃)₂ SiO, and D'=CH₃ (H)SiO

40HA1500-OMe=methyl capped allyl random polyether with 40wt % ethyleneoxide (EO)/60 wt % propylene oxide (PO)--1500 Daltons number averagemolecular weight (mw)

40HA4000-OMe=methyl capped allyl random polyether with 40 wt % ethyleneoxide (EO)/60 wt % propylene oxide (PO)--4000 Daltons mw

40HA1500-OAc=Acetoxy-capped allyl random polyether with 40 wt % ethyleneoxide (EO)/60 wt % propylene oxide (PO)--1500 Daltons mw

40HA4000-OAc=Acetoxy-capped allyl random polyether with 40 wt % ethyleneoxide (EO)/60 wt % propylene oxide (PO)--4000 Daltons mw

Example 1 (Comparative)

To a 4-necked, round bottom flask, equipped with a stirrer, Friedrichcondenser, a temperature-controller and a sparge tube the followingmaterials were charged: 133.3 grams of allyloxypolyethylene glycol(APEG) (385 mw), 66.8 grams of equilibrated methyl hydrogen polysiloxanefluid having a nominal structure of MD₁₅ D'₆ M, 0.09 grams (500 ppm)sodium propionate. The flask contents were agitated and heated to 85° C.reaction temperature with a light nitrogen sparge. At the 85° C.temperature, heating and nitrogen sparge were stopped and the reactionwas catalyzed with 0.28 cc of 3.3% chloroplatinic acid solution inethanol (15 ppm Pt). Within 30 minutes the reaction exothermed and theflask temperature peaked at 117° C. This one-pot batch reaction produceda clear haze-free product of 344 cstk and afforded an aqueous cloudpoint of 50° C. No residual Silanic hydrogen was detected in theproduct.

Example 2 (Comparative)

To a 4-necked, round bottom flask, equipped with a stirrer, Friedrichcondenser, a temperature-controller and a sparge tube the followingmaterials were charged: 72.7 grams of 40HA1500-OMe, 75.3 grams of40HA4000-OMe, 52.0 grams of equilibrated methyl hydrogen polysiloxanefluid having a nominal structure of MD₇₀ D'₅ M. The flask contents wereagitated and heated to 85° C. reaction temperature with a light nitrogensparge. At the 85° C. temperature, heating and nitrogen sparge werestopped and the reaction was catalyzed with 0.29 cc of 3.3%chloroplatinic acid solution in ethanol (15 ppm Pt). Within 35 minutesthe reaction exothermed and the flask temperature peaked at 94° C. Thisone-pot batch reaction produced a clear haze-free product of 1821 cstkand afforded an aqueous cloud point of 37° C. No residual silanichydrogen was detected in the product.

Example 3 (Comparative)

To a 4-necked, round bottom flask, equipped with a stirrer, Friedrichcondenser, a temperature-controller and a sparge tube the followingmaterials were charged: 73.45 grams of 40HA1500-OAc, 76.15 grams of40HA4000-OAc, 50.4 grams of equilibrated methyl hydrogen polysiloxanefluid having a nominal structure of MD₇₀ D'₅ M. The flask contents wereagitated and heated to 80° C. reaction temperature with a light nitrogensparge. At the 80° C. temperature, heating and nitrogen sparge werestopped and the reaction was catalyzed with 0.29 cc of 3.3%chloroplatinic acid solution in ethanol (15 ppm Pt). Within 15 minutesthe reaction exothermed and the flask temperature peaked at 81° C. Thisone-pot batch reaction produced a clear haze-free product of 3328 cstkand afforded an aqueous cloud point of 36° C. No residual silanichydrogen was detected in the product.

Example 4

In a steady state operation, 1333.4 grams/hour of allyloxypolyethyleneglycol (APEG, 385 mw, containing 500 ppm sodium propionate suspended,same lot of material used in Example 1) was fed into the firstcontinuous stirred reactor 5 apparatus shown in the FIGURE throughpipeline 2 and 667.5 grams/hour of equilibrated methyl hydrogenpolysiloxane fluid having a nominal structure of MD₁₅ D'₆ M (same lot asused in Example #1), was fed in over pipeline 1. The temperature of theallyloxypolyethylene glycol being fed through pipeline 2 was maintainedabout 85° C. and the organohydrogenpolysiloxane fluid through pipeline 1about 28° C. The agitated reaction in the first CSTR 5 was catalyzedcontinuously with a 1% chloroplatinic acid solution in ethanol at a rateof 9.9 ml/hour which afforded a constant concentration of 15 ppm ofplatinum in the first CSTR 5 through pipeline 3. Because of thecontinuous hydrosilation reaction exotherm, the CSTR 5 was maintained ata constant temperature of approximately 85-90° C. by the use of anexternal jacket on the first CSTR 5 that could add or remove heat. Thereaction mixture was pumped out of the first CSTR 5 at the same rate atwhich it entered the first CSTR 5 (2010.8 grams/hour) through pipeline 6and into a second CSTR 7. The temperature in the second CSTR 7 wasmaintained at 85-90° C. by the use of an external heated or cooledjacket on the second CSTR 7. The reaction mixture left the secondstirred reactor with a temperature of 85-90° C. through pipeline 8 as ahomogenous clear liquid at a rate of 2010.8 grams/hour and entered theplug flow reactor 9. The heating and cooling mantle of the plug flowreactor 9 was controlled so that the reaction mixture, emerging throughpipeline 10, had a temperature of 85-90° C. The average residence timein the combined volume of the three reactors was 4.0 hours. The reactionproduct optionally was conveyed to a thin-film evaporator 11 in whichthe product was devolatilized under reduced pressure. The resultingproduct was cooled to <50° C. in a heat exchanger 14 and optionallyfiltered (not shown) to product storage 15 via pipeline 13. Thecopolymer product thus prepared was a clear haze-free liquid affording aviscosity of 332 cstk and an aqueous cloud point of 57° C. No residualsilanic hydrogen was detected in the product.

Example 5

In a steady state operation, 2956.8 grams/hours of a homogenous mixturecomposed of 49.1 weight percent 40HA1500-OMe and 50.9 weight percent40HA4000-OMe (same lots of material used in Example 2) was fed into thefirst continuous stirred reactor (CSTR 1) apparatus shown in the FIGUREthrough pipeline 2 and 1040.2 grams/hour of equilibrated methyl hydrogenpolysiloxane fluid having a nominal structure of MD₇₀ D'₅ M, (same lotas used in Example #2) was fed in over pipeline 1. The temperature ofthe allyloxypoly(oxyethylene)(oxypolypropylene) being fed throughpipeline 2 was maintained about 85° C. and the methyl hydrogenpolysiloxane fluid of pipeline 1 about 28° C. The agitated reaction inthe first CSTR 5 was catalyzed continuously with a 1% chloroplatinicacid solution in ethanol at a rate of 33 ml/hour which afforded aconstant concentration of 25 ppm of platinum in the first CSTR 5 throughpipeline 3. Because of the continuous hydrosilation reaction exotherm,the first CSTR 5 was maintained at a constant temperature ofapproximately 85-90° C. by the use of an external jacket on the firstCSTR 5 that could add or remove heat. The reaction mixture was pumpedout of the first CSTR 5 at the same rate at which the combined rawmaterials were entering (4030 grams/hour) through pipeline 6 and enteredthe second CSTR 7. The temperature of the second CSTR 7 was maintainedat 85-90° C. by the use of an external heated and cooled jacket on thefirst CSTR 7. The reaction mixture left the second stirred reactor 7with a temperature of 85-90° C. through pipeline 8 as a homogenous clearliquid at rate of 4030 grams/hour and entered the plug flow reactor 9.The heating and cooling mantle of the plug flow reactor 9 was controlledso that the reaction mixture, emerging through pipeline 10, had atemperature of 85-90° C. The average residence time of the reactionmixture was about 2.0 hours. The reaction product optionally wasconveyed to a thin-film evaporator 11 in which it was devolatilizedunder reduced pressure. The resulting product was cooled to <50° C. in aheat exchanger 14 and optionally filtered (not shown) to product storage15 via pipeline 13. The copolymer product thus prepared was a clearhaze-free liquid affording a viscosity of 1867 cstk and an aqueous cloudpoint of 38° C. No residual silanic hydrogen was detected in theproduct.

Example 6

In a steady state operation, 2993.3 grams/hours of a homogeneous mixturecomposed of 49.1 weight percent 40HA1500-OAc and 50.9 weight percent40HA4000-OAc (same lots of material used in Example 3) was fed into thefirst continuous stirred reactor 5 apparatus shown in the FIGURE throughpipeline 2 and 1008.5 grams/hour of equilibrated methyl hydrogenpolysiloxane fluid having a nominal structure of MD₇₀ D'₅ M, (same lotas used in Example #3) was fed in over pipeline 1. The temperature ofthe allyloxypoly(oxyethylene)(oxypolypropylene) being fed throughpipeline 2 was maintained about 85° C. and the methyl hydrogenpolysiloxane fluid of pipeline 1 about 28° C. The agitated reaction inthe first CSTR 5 was continuously catalyzed with a 1% chloroplatinicacid solution in ethanol at a rate of 33 ml/hour which afforded aconstant concentration of 25 ppm of platinum in the first CSTR 5 throughpipeline 3. Because of the continuous hydrosilation reaction exotherm,the first CSTR 5 was maintained at a constant temperature ofapproximately 85-90° C. by the use of an external jacket on the firstCSTR 5 that could add or remove heat. The reaction mixture was pumpedout of the first CSTR 5 at the same rate at which the combined rawmaterials are entering (4034.8 grams/hour) through pipeline 6 and entersthe second CSTR 7. The temperature of the second CSTR 7 was maintainedat 85-90° C. by the use of an external heated and cooled jacket on thesecond CSTR 7. The reaction mixture left the second stirred reactor 7with a temperature of 85-90° C. through pipeline 8 as a homogeneousliquid at rate of 4034.8 grams/hour and entered the plug flow reactor 9.The heating and cooling mantle of the plug flow reactor 9 was controlledso that the reaction mixture, emerging through pipeline 10, had atemperature of 85-90° C. The average residence time of the reactionmixture was about 2.0 hours. The reaction product optionally wasconveyed to a thin-film evaporator 11 in which it was devolatilizedunder reduced pressure. The resulting product was cooled to <50° C. in aheat exchanger 14 and optionally filtered (not shown) to product storage15 via pipeline 13. The copolymer product thus prepared was a clearhaze-free liquid affording a viscosity of 2822 cstk and an aqueous cloudpoint of 37° C. No residual silanic hydrogen was detected in theproduct.

These data show a more water soluble (by cloud point) copolymer isobtained by the continuous process which is beneficial for personal careapplications. The copolymer made by the continuous process also producedmore open cell foam than standard batch copolymers.

                                      TABLE 1                                     __________________________________________________________________________                                          Foam Test                               Example                                                                            Process         Viscosity                                                                          Cloud       Conc                                                                             Rise                                                                             AF                                Number                                                                                  Type                                                                                              Point, ° C.                                                              Application                                                                            pphp                                                                            cm                                                                                ft.sup.3 /sec                                                                   ST                           __________________________________________________________________________    1    Batch APEG 350  344  50   Personal Care                                                                        -- -- --  --                            4         Continuous                                                                            APEG 350                                                                                       Personal Care                                                                      --                                                                                         --                       2                40HA1500/4000-OMe                                                                      1821                                                                                   Urethane Foam                                                                      0.5                                                                             36.8                                                                               7.9                                                                                6                                                                0.8                                                                              39.0                                                                               5.9                                                                                6                         5         Continuous                                                                        40HA1500/4000-OMe                                                                         1867                                                                                   Urethane Foam                                                                      0.5                                                                             34.8                                                                               8.2                                                                                7                                                                0.8                                                                              37.8                                                                               8.7                                                                                6                         3                40HA1500/4000-OAc                                                                      3328                                                                                   Urethane Foam                                                                      0.5                                                                             37.6                                                                               7.2                                                                                7                                                                0.8                                                                              40.0                                                                               6.7                                                                                6                         6         Continuous                                                                        40HA1500/4000-OAc                                                                         2822                                                                                   Urethane Foam                                                                      0.5                                                                             34.8                                                                               8.8                                                                                5                                                                0.8                                                                              37.8                                                                               9.3                                                                                5                         __________________________________________________________________________

What is claimed is:
 1. A process comprising:(a) continuously feedinghydrogen siloxane, one or more olefinic compounds reactive towards saidhydrogen siloxane, and catalyst for said reaction, to the first in aseries of at least one continuously stirred tank reactor (CSTR), andcontinuously withdrawing from the last CSTR in said series a crudeproduct stream that contains siloxane copolymer and unreacted hydrogensiloxane moieties and olefinic compound; (b) continuously feeding theproduct stream of step (a) to at least one plug flow reactor wherein aproduct stream is withdrawn continuously wherein the reactions of steps(a) and (b) are catalyzed by a noble metal catalyst.
 2. The process ofclaim 1 wherein the hydrogen siloxane and said olefinic compounds arereacted in said series of CSTRs to a sufficient extent that said crudeproduct stream is sufficiently homogeneous that the crude product streamdoes not undergo phase separation in step (b).
 3. The process of claim 2wherein there are at least two CSTRs.
 4. The process of claim 3 whereinthe stream exiting the next to last of said series of CSTRs ishomogeneous.
 5. The process of claim 3 further comprising feeding one ormore of hydrogen siloxane, olefinic compound, and catalyst, to thesecond CSTR in said series.
 6. The process of claim 5 wherein hydrogensiloxane is fed to said second CSTR that is different from the hydrogensiloxane fed to said first CSTR.
 7. The process of claim 5 wherein theolefinic compound or compounds that is fed to said second CSTR isdifferent from the olefinic compound or compounds fed to said firstCSTR.
 8. The process of claim 1 wherein said hydrogen siloxane comprisesany combination of siloxane units selected from the group consisting ofR₃ SiO_(1/2), R₂ HSiO_(1/2), R₂ SiO_(2/2), RHSiO_(2/2), RSiO_(3/2),HSiO_(3/2) and SiO_(4/2), provided that the hydrogen siloxane containssufficient R-containing siloxane units to provide from 1.0 to 3.0 Rradicals per silicon atom and sufficient H-containing siloxane units toprovide from 0.01 to 1.0 silicon-bonded hydrogen atoms per silicon atomand a total of R radicals and silicon-bonded hydrogen atoms of from 1.5to 3.0 per silicon atom, and each R group is independently the same ordifferent and each represents a C₁ to C₁₂ alkyl radical, acycloaliphatic radical containing 5 to 12 carbon atoms, or a phenylradical optionally substituted with 1 to 6 alkyl groups of up to 6carbon atoms.
 9. The process of claim 8 wherein each R is methyl. 10.The process of claim 8 wherein each said olefinic compound is anolefinically substituted block or random polyoxyalkylene correspondingto the formula R¹ (OCH₂ CH₂)_(v) (OCH₂ CHR³)_(w) --OR² wherein R¹denotes an alkenyl group containing 3 to 10 carbon atoms; each R³ isindependently methyl or ethyl; R² denotes a monovalent organic group;and the subscript v has a value of 0 to 200 and the subscript w has avalue of 0 to 200, provided that the sum of (v+w) is greater than
 0. 11.The process of claim 10 wherein R² denotes hydrogen or an alkyl oralkenyl group containing 1 to 5 carbon atoms, a 2-oxacycloalkyl group of4 to 6 carbon atoms, an acyl group containing 2 to 5 carbon atoms, or atrialkylsilyl group.
 12. The process of claim 10 wherein R³ is methyl.13. The process of claim 10 wherein R¹ is allyl.
 14. A process accordingto claim 3 wherein there is a recycle stream from the outlet to theinlet of at least one CSTR.
 15. A process according to claim 1 whereinan [AB]_(n) copolymer is made.
 16. A process according to claim 15 inwhich each said hydrogen siloxane comprises any combination of siloxaneunits selected from the group consisting of R₂ HSiO_(1/2) and R₂SiO_(2/2), provided that each R group is independently the same ordifferent and each represents a C₁ to C₁₂ alkyl radical, acycloaliphatic radical containing 5 to 12 carbon atoms, or a phenylradical optionally substituted with 1 to 6 alkyl groups of up to 6carbon atoms.
 17. A process according to claim 15 wherein each saidolefinic compound is an olefinically substituted block or randompolyoxyalkylene corresponding to the formula R¹ (OCH₂ CH₂)_(v) (OCH₂CHR³)_(w) --OR¹ wherein R¹ denotes an alkenyl group containing 3 to 10carbon atoms; each R³ is independently methyl or ethyl; and thesubscript v has a value of 0 to 200 and the subscript w has a value of 0to
 200. 18. A process according to claim 5 wherein at least one of theolefinic compounds is a hydrocarbon or substituted hydrocarbon.
 19. Aprocess according to claim 16 wherein a second different olefiniccompound is added to a second reactor in the CSTRs.
 20. A processaccording to claim 16 wherein the same olefinic compound is added to allCSTRs in the series of CSTRs.
 21. A process according to claim 3 whereinthe series of CSTRs contains two CSTRs.
 22. A process according to claim1 wherein the series of CSTRs contains one CSTR.